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Symptoms of Drunk Driving

When conducting traffic stops and DUI investigations, law enforcement officers are often looking for certain symptoms that are consistent with drunk driving. Studies have shown that drivers exhibiting the following symptoms often have a high likelihood of being under the influence of drugs or alcohol:

The National Highway Traffic Safety Administration (“NHTSA”) has found that drivers who are observed making wide radius turns or straddling center or lane markers have a 65 percent chance of being intoxicated. These drivers have difficulty maintaining their lane, especially while making turns, and this kind of driving conduct often sends a clear message to law enforcement officers that the driver may be under the influence.

Drivers who nearly strike objects or vehicles or who are observed weaving have been shown to have a 60 percent chance of being impaired. If an officer sees a driver hit or nearly hit an object or vehicle, that driver will likely be pulled over and investigated for a DUI offense if the officer notices physical symptoms of intoxication, such as bloodshot and watery eyes, an odor of alcohol or slurred speech.

Drivers who are seen driving outside of the designated roadways or who are swerving have a 55 percent chance of intoxication. Drivers who are driving 10 mph over the speed limit, who are seen drifting in traffic or who stop in traffic for no reason have a 50 percent chance of intoxication. According to the NHTSA study, drivers who follow too closely, who drive with their tires on the center marker or lane markers, who brake excessively and erratically or who drive against traffic have been shown to have a 45 percent chance of intoxication.

Using one’s turn signal inconsistently with the corresponding driving action has a 40 percent likelihood of intoxication. Responding too slowly to traffic signals, stopping inappropriately and making abrupt or unlawful turns has been shown to have a 35 percent chance of intoxication. Accelerating and decelerating suddenly and driving without headlights in the dark have a corresponding 30 percent likelihood that the driver is impaired.

Even if an officer suspects that a driver is under the influence of drugs or alcohol, the officer must observe a violation of the Vehicle Code or other law in order to justify pulling the driver over. The officer may suspect that the driver is impaired, but if the stop is conducted without reasonable or probable cause the driver may be able to challenge the validity of the stop in court. The defendant can file a motion to suppress pursuant to California Penal Code Section 1538.5. During the 1538.5 hearing, the judge will consider dash cam video of the vehicle stop or other evidence showing why the stop was improper. If the judge finds that stop was made without reasonable or probable cause, the defendant’s motion to suppress will be granted and all subsequent DUI evidence will be thrown out. Typically, the prosecutor will dismiss the case in these situations because he or she will be unable to proceed to trial.